As a device for measuring inner diameter of a hollow member or a hollow shaft, a device disclosed in the Patent Document 1, for example, is already known.
In the inner diameter measuring device as disclosed in the Patent Document 1, a pipe to be inspected is rotatably supported by a pipe rotation supporting device, and a running carriage device has a pair of inner diameter measuring sensors at upper and lower positions, being provided in such a manner that the pair of inner diameter measuring sensors can be brought closer to or separated from each other. By the moving of the running carriage device, the inner diameter measuring sensors are inserted in a pipe to be inspected, and the inner diameter measuring sensors are separated in upper and lower directions and are brought into contact with the inner surface of the pipe to be inspected. Further, the pipe to be inspected is rotated by a pipe rotation supporting device, and the inner diameter of the pipe to be inspected is measured.
The inner diameter measuring device as described above is designed in such structure that a pipe rotation supporting device for rotating the pipe to be inspected has a driving unit and the running carriage device is moved and a pair of inner diameter measuring sensors move up and down, and therefore has a complex structure. Further, inner diameter measurement is limited to a range where the inner diameter measuring sensors can be inserted. As a result, there is a problem in that the inner diameter of the pipe to be inspected cannot be measured if the pipe to be inspected has a longer axis.
To solve the problems as described above, it is an object of the present invention to provide an inner diameter measuring device, which is designed in simple structure and by which it is possible to perform a measurement of the inner diameter of a hollow pipe.